This invention relates to apparatus for the thermic or non-catalytic afterburning of exhaust gases and the simultaneous muffling of internal combustion engines.
It is known to arrange exhaust gas afterburning devices in the exhaust system of internal combustion engines, especially motor vehicle engines, to burn the exhaust gas before its discharge into the atmosphere to decrease as much as possible the portion of the harmful substances contained in the exhaust gas, especially carbon monoxide and unburned hydrocarbons.
In known thermic afterburning devices, the exhaust gas to be afterburned enters into an essentially tube-shaped combustion chamber from an exhaust pipe. The exterior side of the combustion chamber is surrounded by a shell space which is supplied with cooling air from a blower, for example. The downstream end of the cooling air shell opens into the atmosphere and is connected with the combustion chamber in such a way that heated cooling air flows into the combustion chamber as additional or secondary air for the afterburning of the exhaust gas. The hot afterburned exhaust gas is carried off from the combustion chamber over a relatively long pipe which is connected to it. Such afterburner construction has the disadvantage that the afterburned gas enters the atmosphere at an extremely high temperature of, for example, 500.degree. - 800.degree. C, and the entire device is relatively long. Also known are thermic afterburning devices in which the afterburned exhaust gas exits from an annularly-shaped combustion chamber, and is limited by the combustion chamber and a housing shell surrounding the combustion chamber flows along the combustion chamber to the end opposite the end where it entered and discharges into the atmosphere. Here, the housing shell is only cooled by the ambient air. In such a construction, the afterburned exhaust gas flowing along the combustion chamber maintains high temperatures in the combustion chamber walls which assists the afterburning of the exhaust gas, but there is also the disadvantage that the afterburned exhaust is discharged into the atmosphere at a high temperature. Additionally, the afterburner is expensive because the housing shell surrounding the combustion chamber has to withstand high temperatures and must therefore be made of an expensive high-temperature resistant material.